1. Field
A liquid crystal display module that prevents a wrinkle of an optical sheet is provided.
2. Related Art
A CRT (cathode ray tube) is a display device that can be used in, for example, a monitor of a measuring instrument, an information terminal, and a TV. However, the CRT's large weight and size is not beneficial to the demand of does not an electronic appliances smaller and lighter.
The display devices that are expected to replace the CRT include, for example, a liquid crystal display LCD using an electric field optical effect, a plasma display panel PDP using a gas discharge, an organic light emitting diode OLED using an field effect luminous effect.
The liquid crystal display device that has advantages such as compact size, light weight and low power consumption has recently been developed to act as a flat panel display. The LCD is used, for example, in desktop computer monitors and notebook computer monitors, thus the demand for the liquid crystal display device is continuously increasing.
Because the liquid crystal display device is not a self-luminous display device the LCD needs a separate light source, for example, a backlight unit. The liquid crystal display device includes a liquid crystal display module includes a backlight unit and a liquid crystal display panel that realizes a picture by use of the light from the backlight unit. A drive circuit part drives the liquid crystal display module.
As shown in FIG. 1, a liquid crystal display module of the related art includes a light source 9. A light guide panel 11 converts the light from the light source into a surface light. A housing 10 receives the light source 9 and has an opening part opened to a light incidence surface side of the light guide panel 11. A main support 1 encompasses the side surface and upper surface of the housing 10 and supports the liquid crystal display panel. A backlight unit includes a plurality of optical sheets 8 disposed on the light guide panel 11 and a reflection plate 12 installed to face the lower surface of the light guide panel 11. A liquid crystal display panel 7 irradiates the light from the backlight unit to display a picture. A case supports the whole liquid crystal display module and protects the liquid crystal display module from an external impact. A cover bottom 12 and a case top 2 being a sash member.
The liquid crystal display panel 7 includes an upper plate 3 where a black matrix, a color filter array, a common electrode and an alignment film are sequentially formed on a substrate. A lower plate 4 has a TFT array, a pixel electrode and an alignment film sequentially formed on a substrate. An upper polarizer 5 is disposed on the upper plate. A lower polarizer 6 is disposed under the lower plate. A spacer (not shown) maintains a gap between the upper plate and the lower plate. A liquid crystal layer is injected into a space between the upper/lower plates 3, 4. The upper and lower plates 3, 4 are bonded together by a sealant.
The backlight unit includes a light source 9. A light guide panel 11 converts the light from the light source into a surface light. A housing 10 receives the light source 9 and an opening part opened to a light incidence surface side of the light guide panel 11. A support main 1 encompasses the side surface and upper surface of the housing 10 and supports the liquid crystal display panel. A plurality of optical sheets 8 are disposed on the light guide panel 11. A reflection plate 12 is installed to face the lower surface of the light guide panel 11.
The light source generates light. A cold cathode fluorescent lamp CCFL, a hot cathode fluorescent lamp (HCFL), an external electrode fluorescent lamp (EEFL), a light emitting diode (LED) may be used as such a light source 9.
The light guide panel 11 converts the incident light from the light source 9 through the light incidence part of the side surface into a surface light. The light guide panel 11 is generally formed of a transparent acryl resin that has high strength so as not to be broken or deformed easily.
The housing 10 of a metal material is formed to have a shape that encompasses the light source 9. The reflection plate is bonded to the inner surface, or a metal of a reflective material is coated on the inner surface in order to reduce the loss of the light that is incident from the light source 9 to the light guide panel 11.
The reflection plate 12 is located in the lower part of the light guide panel 11 to reflect the light that progresses to the lower surface of the light guide panel 11 and to the upper surface of the light guide panel, thereby reducing light loss.
Optical sheets 8 are located between the light guide panel 11 and the liquid crystal display panel 7. The optical sheets 8 uniformly disperse the light from the light guide panel 7 to the picture display part of the liquid crystal display panel 7 that is supplied thereto, and increases light efficiency. The optical sheets 8 are disposed on the upper part of the light guide panel 11. The optical sheets 8 include a diffusion sheet that makes a picture that is displayed in the liquid crystal display panel 7 have an evenly-distributed brightness by way of making the incident light from the light guide panel 11 dispersed to the whole surface of the picture display part of the liquid crystal display panel 7 to be supplied thereto. A prism sheet increases the brightness of the picture displayed in the liquid crystal display panel 7 by making the incident light from the diffusion sheet process in a fixed direction by an angle and a pitch of a prism shape. A protection sheet protects the prism sheet.
The main support is encompasses the upper surface and side surface of the housing 10, the edge of the upper surface of the light guide panel 11 and the edge of the optical sheets 8. The main support fixes the optical sheets 8 and supports the the liquid crystal display module. The main support 1 is formed of a plastic material by molding.
The bottom cover 13 is installed to encompass the lower surface of the liquid crystal display module and the side surface of the main support 1. The bottom cover 109 is formed of a metal material, for example, aluminum.
The top case 2 is installed to encompass the upper surface and side surface of the main support 1 and the edge of the liquid crystal display panel 7, and is combined with the cover bottom 13 in the side surface of the main support 1. The top case 2 encompasses the edge of the liquid crystal display panel 7 to protect the liquid crystal display panel from an external impact.
The optical sheets 8 are deposited on the light guide panel 11 and are fixed with a pressure applied thereto by a projected part of the main support 1. There are many cases that a gap is generated between the light guide panel 11 and the main support 1 due to the material of the main support 1 being made from plastic.
As shown in FIG. 2, when a gap exist, a wrinkle 14 is formed in the optical sheets 8. FIG. 2 represents a cross section of a liquid crystal display module, cut along the line A-A′. If the wrinkle 14 is formed in the optical sheets 8 the picture displayed in the liquid crystal display panel 7 is distorted at a location where the wrinkle 14 is formed, as shown in FIG. 3, thereby deteriorating picture quality. The wrinkle 14 formed in the optical sheets 8 is connected to a defect of a product in accordance of the degree thereof. The defect of the product decreases its yield, the defect thus creates a cost increase. The product that has a defect caused by the wrinkle 14 is considered a good product and is distributed; however, the picture quality deteriorated by the wrinkle 14 lowers the reliability of the product.